Sorption of bisphenol A, 17α-ethynylestradiol and estrone to mineral surfaces

Sorption of the endocrine disrupting chemicals (EDCs) bisphenol A (BPA), 17α-ethynylestradiol (EE2) and estrone (E1) from 3 μM aqueous solutions in 10 mM KNO3 to goethite, kaolinite and montmorillonite was investigated at 25 °C. Uptake of the EDCs by goethite and kaolinite suspensions was <20%, and little affected by pH. Sorption by montmorillonite was greater, ranging from 20 to 60%, and steadily increased from about pH 7. The amount of EDC sorbed to the mineral phases generally increased in the order of decreasing solubility (BPA < EE2 < E1). Sorption to goethite and kaolinite was rapid (<10 min), but much slower for montmorillonite, to which sorption continued for 24–48 h. Although the EDCs desorbed rapidly and completely from goethite and kaolinite, only small amounts desorbed from montmorillonite below pH 7, and no recovery was observed at pH 10. The kinetic and desorption experiments indicate that the EDCs intercalate into the interlayer spaces of montmorillonite, but for goethite and kaolinite sorption probably occurs at external surfaces.

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